High temperature cobalt-base and nickel-base superalloys are used in the manufacture of components for the high temperature sections of gas turbine engines. Such components, which include nozzles, combustors, and turbine vanes and blades, are under strenuous high temperature conditions during engine operation, which can lead to various types of damage or deterioration. For example, erosion, cracks and other surface discontinuities tend to develop at the trailing edges of blades and nozzles during service due to foreign object impact and stresses that are aggravated by frequent thermal cycling. Because the material and processing costs of high-temperature superalloys is relatively high, restoration and repair of damaged or worn superalloy components are typically preferred over replacement. For this purpose, weld repair methods have been developed using tungsten inert gas (TIG) or laser welding processes, which are typically performed at an elevated temperature (e.g., in excess of about 1500.degree. F. (about 815.degree. C.)) to improve welding yields and ensure that the mechanical properties of the superalloy are maintained. To prevent oxidation, high-temperature weld repairs of superalloys are often performed in enclosures containing a controlled atmosphere, e.g., an inert gas such as argon.
A complication exists when welding repairing a crack in the wall of a hollow component, such as an air-cooled blade or nozzle having an interior cooling cavity or passage. During welding, the cooling passages of these components are susceptible to blockage by weld filler material that enters the passages through the cracks being repaired. An example is shown in FIG. 1, which shows a nozzle 10 that must be assembled with an insert 12 that closely fits within a cooling passage 14 of the nozzle 10. Any weld filler material that enters the cooling passage 14 has the potential for blocking the passage 14 or causing interference with the insert 12. While methods for blocking surface cooling holes 22 (typically at the trailing edge 28 of the nozzle airfoil 24) are known, a difficulty remains in providing for complete filling of a crack 30 without weld filler also entering the passage 14 through the crack 30.